Stylus mounting



July 21, 1942. w. G. H. FlNCH 2,290,230

STYLUS MOUNTING Filed Aug. 16, 1940 4 Sheets-Sheet l FIGJ.

1NVE NTOR.

William fate/1 ATTORNEY.

i 1942- w. G. H. FINCH 2,290,230

STYLUS MOUNTING Filed Aug. 16, 1940 4 Sheets-Sheet 2 W l 1 I IL INVENTOR Whammy. Woke/t July 21, 1942. w. G. H. FINCH STYLUS MOUNTING 4 Sheets-Sheet 5 INVENTOR.

Filed Aug. 16, 1940 July 21, 1942. w. G; H. FlNCH STYLUS MOUNTING Filed Aug. 16, 1940 4 Sheets-Sheet 4 FIG. 5.

FIG.6.

INVENTOR.

ATTORNEY.

Patented July 21, 1942 UNITED jsTATi-zs' PATENT OFFICE william li Conn.

Application August 16, 1940, Serial No. sszss'z' 11 Claim.

This invention relates to facsimile apparatus and more particularly to a scanning system for a facsimile receiver wherein scanning members are mounted upon a continuous belt and successively brought into cooperation with the sheet upon which the received signals are to be recorded.

to a form of mounting of the scanning members which will simplify the synchronization'of the receiver with the transmitter while at the same time facilitating the operation of the entire mechanism. I

This application, therefore, is a continuation inpart of my application Serial No. 334,404, filed May 10, 1940, which disclosesa type of slidable mounting for scanning members upon a chain drive.

Where the scanning member is slidably positioned on a mounting of restricted length, which in turn is carried by a chain drive, then during the course of reception, it maybecome necessary to rephase the apparatus to reposition the scanning member on its mounting. 'This is done to prevent the scanning member from being forced off its mounting by successive synchronizing operations which may have a cumulative-effect. The repositioning of the stylus in respect to its mounting, in such apparatus where the mount ing is of restricted length, should occur at the end of every scanning cycle. The purpose of the rephasing operation which maybe performed either before picture reception has commenced or which may be performed only once or twice during picture reception is to reposition the entire stylus mechanism in its mounting in such a way that the successive slidings of the stylus in its mounting at the end of each scanning cycle will not cause the stylus to be removed from the mounting.

An object of the present invention is to so arrange the driving means, the stylus and the stylus mounting, that the stylus, in effect, has a mounting of unrestricted length. 7

A further object of the present invention.

' therefore, is to provide in apparatus where a stylus is mounted upon a continuous member, a mounting for the stylus which will permit the stylus to be moved to any position which it must assume during picture reception .without the necessity for any automatic or manual reposition of the stylus.

Still another object of the present invention is the provision of a mounting for a stylus, in a continuous driving mechanism, which will permil. synchronization to take place at-the stylus member itself by a halting of the said stylus member without interfering with the operation or continued movement of the stylus mounting, the stylus drive or the remainder of the apparatus.

It should be noted that the essential portion of the present invention which is a continuation in part of my application 8. N. 334,404, above mentioned is to reduce the masses which must be brought to a stop and started once during each cycle for synchronization by the construction of my present invention, the actual mass which must thus be brought to a stop is limited to virtually the actual scanning point itself. Even the carrier for the scanning point or memher and the drive for this carrier and all the remainder of the apparatus may be permitted to continue movement during synchronization.

' In the present invention it is not even neces- I ceiver having the scanning system of my present invention.

Figure 2 is a front view partial y broken'away of the apparatus of Fig. 1.

Figure 3 is a view partially in cross-section taken along line 3-3 of Fig. 1. Figure 3a'is an enlargement of a. portion of Fig. 3. a

Figure 4 is a cross-sectional view taken along line 4-4 of Fig. 1.

Figure 5 is a top view corresponding to the lower left-hand comer of Fig. 1.

Figure 6 is a cross-sectional view taken along line 5-3 of Fig. 5.

Referring now to Figures 1 and 2, I have here shown a facsimile receiver corresponding to the facsimile .receivers shown in my applications S. N. 240,675, filed Nov. 16, 1938,. and S. N.

334,404, filed May 10, 1940.

The entire apparatus is supported upon a cast iron base 20 which is suitably mounted and supported'in a cabinet or frame. A motor zl, preferably of a non-synchronous type, is supported beneath the cast iron base and serves to drive the entire facsimile receiving mechanism in the manner. described in my two applications above mentioned.

The sensitized paper 25 is, by the operation of pressure upon the paper 2b and the proper tension on the roll are also clearly and specifically described in the above mentioned applications.

It is sufflcient, for an understanding of the present invention, to point out that during the operation of the motor iii, the paper 25 is continually being moved at a regular rate in the direction indicated by the arrows 30 of Fig. 1.

This movement is relatively slow so as to permit scanning of the sheet by styli which move in a path substantially at right angles to the direction in which the sheet is moving.

This general type of scarming operation is also described in my applications above mentioned and should now be familiar to those skilled in the art.

The specific contribution of the present invention is in the mounting-and operation of the stylus itself and in the synchronization of the gacsimile reception apparatus; this is the only subject matter to which a specific description is here directed.

The scanning mechanism comprisesv a plurality of styli it, preferably three in number, and

' each mounted upon a double belt ilfi2; the

ribbons M and 32 of the belt having the space lii between them.

It should be understood that, during the operation of the mechanism, the ribbons il and 322 of the belt are to act as a unit. The space it between-the two ribbons at and d2 is provided, in order to permit a proper mounting of the stylus so that it may readily be slidable along the belt ilk-t2 in the manner hereinafter described.

Each stylus 38, as is more particularly seen in Figs. 1,3, 30;, and 5, comprises a spring metal member at which is bent along the area 5! to form a base which may be held frictionally tight against the belt 6 IQ2. The spring metal member 5b is bent at 52 into a trolley 53 which carries the rotatable contact point 56 which actually comes into contact with and scans the sensi-' tized sheet 25.

As is seen in Figs. 3 and 3a, the trolley portion 53 isslotted at 56 so that the stylus or rotatable contact point 54 may freely rotate with respect thereto, the said rotatable stylus 54 being journaled in the bearings 57! of the trolley 53. The bend 52 which defines one end of the trolley 53, and the metal of the trolley 53 are resilient, and are so arranged that (as is seen in Fig. 5) the perpendicular distance between the belt fll-ti" and the sensitized sheet 25 is less than the normal distance between the stylus 5t and the belt ll- 52. The resilience of the metal forming the trolley 53 permits the trolley to be bent sufliciently to allow the stylus 56 to be brought into engagement with the sensitized sheet 25 with.

ill

appropriate pressure between the stylus 54 and the sensitized sheet. The base 5i of the stylus member is not rigidly secured to the belt M-42, but is frictionally tight against the said belt.

Such frictional engagement between the mem bers is maintained by the bolts Hi which are secured to the base 55 and pass through the space at between the ribbons M and d2 of the belt. A spring member 112 is secured to the bolts W in any suitable manner as, for instance, by the nuts l3'ltl. The said spring member is so curved as to provide a bearing surface it against the opposite side of the-ribbons ii and 632. p

The belt it- 52 isthus frictionally caught between the base at and the bearing surface M of the spring 712.

This frictional engagement is such as to per mit the entirestylus to slide longitudinally with respect to the belt ill-(i2 when the said stylus is positively held or engaged. That is, when the belt ll-t2 is continuously being moved by the sprockets 8G and 89, if a positive abutment is placed in front of the entire stylus member it, the said stylus member at will come to a stop and thus will slide with respect to the belt Gfl l2.

The frictional engagement, however, between the stylus member til and the belt Mlt is such as to cause the stylus member ill, under normal conditions, to move with the belt; and this frictional engagement is likewise sufficient to cause the said stylus (it to move with the belt M42, even when the contact point or wheel M is in contact with the sensitized sheet 25.

The belt ii-52 is driven in a manner which isnow well-known in connection with chain drive apparatus. That is, the motor shaft 9b is by the ,fiexible coupling 98 connected to the shaft 92,

dil

which through the worm and spiral gears 93 and M drives the vertical shaft 95, which in turn drives the sprocket or pulley ti, which supports and drives one end of the belt (ilk-d2. The opposite sprocket or pulley at is an idler supported .on a shaft 9i! which is carried by the block $8.

. the necessary scanning operation. The drum 21 over which the sensitized paper 25 moves and the belt Alb-t2 carrying the stylus id are connected to opposite poles of an electrical circuit, the current in which is modulated in accordance with the received picture signals; thus providing for the marking of the sensitized sheet by the stylus at in accordance with the received picture signals.

As seen in Figs. 2 and 5 the sprockets or pulleys 8b and M are recessed at H8 in order to provide clearance for the members T12 and E3 of each stylus assembly till. When the portion of the belt ill- 32 carrying the stylus assemblies is brought into contact with said sprockets or pulleys, these members can, owing to the inherent flexibility of their mounting, readily pass around the curve of the pulleys, while the portions i2 and 13 which project beyond the inner side of the belt travel in the recess 1 E6.

The stylus assembly 40 is appropriately guided when it is in contact with the sensitized sheet 25 in the manner shown in Fig. 4. Thus, a pair of wires I20 and I2! (see Figs. 4 and 5) are so end 203 of the synchronizing lever 200 is engaged in the notch 204 of the armature 205 of the synchronizing magnet 200. The armature 205 is pivotally mounted on the pin 201 and is biased tion with the sheet 25, travels in a rail I30 which comprises an upper grooveI3I and a lower groove I32. These grooves positively position the belt 4I-42 and the base of the associated stylus mechanism 40 at a selected distance from the sheet to ensure that stylus pressure is accurately maintained against sheet 25 during the scanning process. in Fig. 4, may be formed from an L -shaped member I33 and a capping member I34 secured thereto by the screws I35 thus providing for simplified assembly of the-apparatus.

An additional rail I30 (similar to rail I30) may be provided at the front of the mechanism where the styli are not in engagement with the sheet 25, in order to prevent possible sagging of the belting although such rail I30 is not necessary to the operation of the apparatus.

In ordinary cases the grooves I3I and I32 in the rail I30 positioning the belt 4I42 should provide suflicient stylus pressure for proper scanning. In the event that the belt is too flexible for this purpose, then the'surface I40 of the rail I30 may be so arranged that it will be in contact with or exert some sliding pressure against curve I4II4I of the spring I2 for this purpose.

The rail I30, as may readily be seen As is seen in Fig. 2, the pulley 8| is insulated by the insulating member I50 from the remainder of the apparatus. The pulley 80 is similarly insulated. .The rails I30 and I30 are insulated from the remainder of the apparatus by the insulating strips I53 and I54 (cf. Fig. 4).

The stylus assembly 40 and the stylus 54 are thus electrically insulated from the remainder of the apparatus. The drum 2'! is electrically connected to the frame of the apparatus and is at ground potential.

Accordingly, current may be caused to flow from the stylus 54 through the sheet 25 to the drum 21, thus marking the sheet in accordance with the variationsin the current.

The principal purpose of the stylus mounting hereindescribed is to obtain synchronization without requiring variations in the movement of many large masses. In the present construction, the only member which must be brought to a stop for synchronization purposes is the stylus assembly 40.

At the inception of each'scanning line, the stylus assembly 40 is brought to a stop to await the synchronizing signal. When the synchronizing signal is received. the stylus assembly is permitted to move with the belt 4I42 for scanning purposes.

When the stylus assembly 40 is brought to a stop by a positive abutment placed in its path, then, owing to the fact that the engagement between the stylus assembly 40 and the belt 4I-42 is only a frictional one, the belt 4I42 may continue to move at undiminished speed with respect to the remainder of the apparatus and with respect to the stylus assembly 40 which has been brought to a stop.

In order to accomplish this purpose, a synchronizing lever 200 is pivotally mounted on the pin 20I so that the engagement end 202 thereof is in the path of the stylus assembly 40 and specifically. is so arranged that it will engage against portion 52 of the stylus assembly. The opposite by a spring 208 so that the notch 204 thereof is brought into engagement with the end 203 of the synchronizing lever. A pin 200 is arranged to limit the movement of the armature 205 under the influence of the spring 208. The end 203 of the synchronizing lever is much heavier than the end 202', thus biasing the synchronizing lever 200 to clockwise movement with respect to Figure 3 and thus tending to bring to a position where it will engage the-notch 204 of the armature. A pin 2I0 is arranged to limit the movement of the end 203 of the synchronizing lever when re-engagement is to be effected.

A cam switch 300 is mounted on the frame 20 for the purpose of switching the incoming sig nals at the conclusion of the scanning line and immediately before the synchronizing signal is to be received. When the stylus assembly 40 reaches the synchronizing lever, it is desirable that the received signals be transferred to the synchronizing magnet 206 rather than to the stylus 54. Immediately upon receipt of the synchronizing signal it then becomes necessary to again energize the stylus 54 while de-energizing the magnet 206. I

Accordingly, the members of cam switch 300 are so arranged that when the central contact member 30I is in contact with the contact member 302,- the incoming signals are transmitted to the stylus 54 and when the central contact member 30I is in contact with the contact member 303, the incoming signals are transferred at the synchronizing magnet 206. The central contact members SM is extended into the arm 304 carrying the chamfered bearing surface 305. When the portion 52 of the'stylus assembly approaches the end 202 of the synchronizing lever, it first depresses the chamfered portion .305 of the arm 304 of the central contact 30I thus dc-.

energizing the stylus 54 and causing the electro- .nizing lever 200 and the entire stylus assembly 40 is brought to a stop while th belt 4I42 continues to move.

Upon receipt of the synchronizing signal, the

" electromagnet 200 is energized thus attracting the armature 205 and thus releasing the end 203 of the synchronizing lever from its engagement with the notch 204 of the armature 205.

Accordingly, there is now no mechanical force preven ing the rotation of the synchronizing lever 200, or consequently preventing the movement 'of the stylus assembly 40 with the belt 4I-42. The stylus assembly 40 therefore, is again permitted to move with the belt and depresses the end 202, the synchronizing lever 200,

' thus rotating the entire synchronizing lever 200 to the position shown by the dotted lines of Figure 3. When the end 202 of the lever 200 is thereafter disengaged from the stylus assembly 40 by the continued movement of the-said stylus assembly 40 with the belt 4I-42 then end 203 of the lever 200 will drop down to engage with notch 204 of the armature 205.

The chamfered surface 2500f the arm 203 and surface 25I of'the armature 205 will facilitate the said re engagement. Should it be necessary, in order to accomplish this engagement, any suitable spring may be utilized in order to insure that the synchronizing lever 200 will return to the position shown by the solid lines of Figure 3.

relation with the said member 302 in order to energize the stylus 54.

By means of the construction of the present invention and by means of the stylus mount of the frictional securement thereof to the belt 4Il2, itis possible to obtain accurate synchronization without bringing any large masses to a' stop at any particular time.

The only member which it is necessary to bring to a stop is the stylus assembly 40 which is relatively light in weight. This stylus assembly is in frictional engagement (not with a mere restricted mounting on a chain drive but) with the entire driving belt so that it may be moved to any position on the belt and thus cannot be disengaged from the belt in any way.

Accordingly, the stylus assembly 40 is in position to operate no matter what its position on the belt may be.

By means of the present construction, it, is possible to operate the receiving apparatus only slightly faster than the scanning apparatus to insure that the stylus assembly will reach the synchronizing lever and be stopped thereby before the synchronizing signal is received. The

cumulative displacement of the stylus assemblyowing to repeated halting thereof for synchronizing purposes at the inception of each scanning line cannot, however, cause the stylus assembly. to be disengaged from the belt or its mounting means.

Accordingly, no rephasing operation is required. It is only necessary to utilize an appropriate synchronizing signal at the beginning of the picture transmission'operation in order to insure that each stylus assembly is brought to proper position for scanning purposes.

In actual operation before the inception of picture reception, it may be desirable to ensure proper spacing of the stylus assemblies with respect to each other, by moving the stylus assemblies relatively close together and relying on the received synchronizing impulses to space them accurately. Thus, if one of the stylus assemblies 40 is in the position of stylus assembly 40a. of Figure 1, then stylus assembly 40b should be moved so that the distance between stylus assembly 40b and stylus assembly 400. is somewhat less than the width of the sheet to be scanned and stylus assembly 400 should be moved to the position where the distance between the said stylus assembly and stylus assembly 40b is also somewhat less than the width of the sheet 25.

When picture reception and recording is to commence, the stylus assembly 40a will be maintained in the position shown in Figure 1 by the synchronizing lever 20!) until the reception of the synchronizing signal; whereupon it will begin to traverse the sheet. Since the lever 200 is returned to abutting position, immediately after the stylus assembly 40a begins its scanning exspect to the moving belt "-42 until the reception of the next synchronizing signal, when its excursion will begin. The same procedure will occur with respect to stylus assembly 400. The

recurrent synchronizing signals will thus serve to properly space theystylus assembly apart at the outset.

Subsequent sliding movements of the stylus assembly with respect to the belt "-42 will be" of a relatively slight character occasioned by the slight increase in speed of the receiving scanning mechanism over the transmitter. Thus while, at the very beginning of picture reception,

each stylus assembly may be required to slide the first three synchronizing signals have been received for the first three scanning lines of the picture, each stylus assembly will be required to slide only a'slight fraction of an inch for synchronizing purposes.

In ordinary operation, after the first picture has been received with a new receiving apparatus, it may not thereafter be necessary to move stylus assembly 4012 closer to stylus assembly 40a, or stylus assembly 400 closer to stylus assembly 401), before other picture signals are receivedsince the stylus assemblies hav been properly spaced by the first three scanning lines of the first picture. This operation however may be followed after a long period of disuse of the mechanism in order to insure that the space be-- tween any two stylus assembliesis not so much greater than the width of the sheet 25, that the stylus assembly will reach the synchronizing lever after a synchronizing signal has been received.

If the stylus assemblies are accidentally spaced incorrectly so that the distance between any two ofthem is much greater than the width of the sheet, they may automatically be spaced properly by a few regularly spaced synchronizing signals sent by the transmitter before actual picture transmission commences.

By reason of the present invention special stylus mountings for the stylus assembly are not necessary. The entire chain or belt drive is the mounting for the stylus, and the stylus assembly may be moved to" or positioned anywhere upon the belt for synchronizing or other purposes.

Rephasing of the mechanism during operation and in order to'prevent the stylus assembly to be disengaged with the mounting is thus no longer necessary and proper phasing of th styli for picture reception at the beginning of a picture is clearly simplified.

By means of the present invention, it is no longer necessary to bring the entire chain drive or belt drive and its sprockets to a stop in order to obtain synchronization; but, rather, only the relatively small .mass of the stylus assembly itself must be brought to a stop. This reduces the mass of the members which must be halted for synchronizing purposes, reduces vibrations and fluttering, and substantially improves the clarity of the received picture.

While I have here described but one type of slidable frictional mounting for my stylus assembly herein, the stylus assembly ma be slidabiy positioned and frictionally held by any appropri- Y 2,290,230 ate formation of its mounting or the drive belt Many other modifications should be obvious to those skilled in the art; thus, for instance, any other type of drive member may be utilized for this purpose, including a chain drive having or carrying appropriate continuous bearing surfaces against which portions of a frictionally mounted stylus assembly may bear.

There are many other modifications of the present invention which should now be clear. Accordingly. I prefer to be.bound not by the specific disclosures herein, but only by the appended claims.

I claim:

1. A telepicture receiver for line by line scanning of a sheet comprising a sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving'said stylus support with respect to said sheet; a stylus element 'slidably carried by said continuous stylus support, synchronizing means responsive to received synchronizing signals for selectively moving said element to any desired section of said stylus support.

2. A telepicture receiver for line by line scanning of a sheet comprising a sheet carrier and "a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; a stylus element frictionally positioned on said continuous stylus support, said element being slidable thereon and being selectively movable toand positionable at any desired section of said stylus support in response to received synchronizing signals.

3. A telepicture receiver for line by line scanning of a sheet comprising a sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to saidsheet; said stylu support comprising a continuous belt; a stylus element frictionally positioned on said continuous stylus support, synchronizing means responsive to received synchronizing signals for periodically moving said element slidable on said belt for maintaining said element in proper phase relation with respect to received picture signals.

4. A telepicture receiver for line by line scanning'of a sensitive sheet comprising a sensitive sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; said stylus support comprising a pair of spaced parallel co-planar continuous ribbons forming a belt having a longitudinal slot therein, a stylus ele- 55 ment friotionally positioned on said continuous stylus support, said element being slidable thereon and being selectively movable to and positionable at any desired section of said stylus support.

5. A telepicture receiver for line by line scan- 6 .ning of a sensitive sheet comprising a sensitive sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; said 65 stylus support comprising a pair of spaced parallel co-planar continuous ribbons forming a belt having a longitudinal slot therein, a stylus element comprising a base member frlctionally secured at a surface of said belt and selectively 70 slidable along said belt; said base carrying a member for contacting said sensitive sheet.

6. A telepicture receiver for line by line scanhim; of a sensitive sheet comprising a sensitive Y sheet carrier and a continuous stylus support, ning of stylus support comprising a pair of spaced par-- allel co-planar continuous ribbons forming a belt having a longitudinal slot therein; a stylus element comprising a base member, said base memher being carried in face to face relation with one surface of each of said ribbons; securing means passing through the longitudinal slot between said ribbons and connecting said base member with a securing member; said ribbons being frictionally captured between said base member and said securing member, said stylus element being frictionally positioned. upon the belt formed by said ribbons and being selectively slidable along said belt.

7. A telepicture receiver for line by line scanning of a sensitive sheet comprising a sensitive sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; said stylus support comprising a pair of spaced par.- allel co-planar continuous ribbons forming a belt having a longitudinal slot therein; a stylus element comprising a base member irictionally secured at a surface of said belt and selectively slidable along said belt; said base carrying a member for contacting said sensitive sheet; said stylus element being normally movable with said belt; and means for halting said stylus element and causing the same to slide with respect to said belt while said belt maintains its regular movement.

8. A telepicture receiver for line by line scanning of a sheet comprising a sheet carrier and a continuous stylus support, mean for regularly uninterruptedly moving saidstylus support with respect to said sheet; said stylus support comprising a continuous belt; a stylus element comprising a base member frictionally secured at a surface of said belt and selectively slidable along said belt; said base carrying a member for contacting said sheet; said stylus element being normally movable with said belt; and synchronizing means responsive to received synchronizing signals for halting said stylus element and causing the same to slide with respect to said belt while said belt maintains its regular movement.

9. A telepicture receiver for line by line scanning of a sensitive sheet comprising a sensitive sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; said stylus support comprising a pair of spaced parallel co-planar continuous ribbons forming a belt having a longitudinal slot therein; a stylus,

0 between said ribbons and connecting said base member with a securing member; said ribbons being frictionally captured between said base member and said securing member, said stylus element being frictionally positioned upon the belt formed by said ribbons and being selectively slidable along, said belt; said stylus element. being normally movable with said belt; and means for halting said stylus element and causing the same to slide with respect to said belt while said belt maintains its regular movement; and means for releasing said halting means'upon the receipt Of a synchronizing signal.

10. A telepicture receiver for line byline scana sheet comprising a sheet carrier and a continuous stylus support, means for regularly uninterruptedly moving said stylus support with respect to said sheet; said stylus support'comprising a continuous belt; a stylus element comprising a base member frictionally secured at a surface of said belt and selectively slidable along said belt; said stylus element being normally movable with said belt, an abutment interposable in the path of said stylus element for halting said stylus element before inception of a scanning cycle and causing the sam to slide with respect to said belt while said belt maintains its regular movement; and means responsive to received synchronizing signals for removing said abutment to again permit said stylus element to move with said belt.

11. A telepicture receiver for line by line scanning 01' a sensitive sheet comprising a sensitive sheet carrier and a continuous stylus support,

means for regularly uninterruptedly moving said stylus support with respect to said sheet; said stylus support comprising a continuous belt; a stylus element comprising a base member frictionally secured at a surface of said belt and selectively slidable along said belt; said base carrying a member for contacting said sensitive sheet; said stylus element being normally movable with said belt and an abutment interposable in the path of said stylus element tor halting said stylus element before the inception of a scanning cycle and causing the same to slide with respect to said belt while said ,belt maintains its regular movement; and means for removing said abutment from abutting relation with said stylus element upon receipt of a synchronizing signal and permitting said stylus to move with said belt to scan said sheet.

' WILLIAM G. H. FINCH. 

